Vibration-insensitive fiber spool for laser stabilization

Excess frequency noise induced by mechanical vibration is the dominant noise source at low Fourier frequencies in fiber-delay-line stabilized lasers. To resolve this problem, a double-winding fiber spool is designed and implemented that has ultralow acceleration sensitivity in all spatial directions. By carefully choosing the optimal geometry parameters of the fiber spool, we achieve acceleration sensitivity of 8 × 10~(-11)/g and 3 × 10~(-11)/g(g denotes the gravitational acceleration) in axial and radial directions, respectively.     

Observation of the ~1S_0-~3P_0 optical clock transition in cold ~(199)Hg atoms

We report on the observation of the highly forbidden ~1S_0–~3P_0 optical clock transition in laser-cooled ~(199) Hg atoms.More than 95% depletion of cold ~(199)Hg atoms is detected in the magneto-optical trap. Using the free-of-field detection method, the AC Stark shift from the cooling laser is removed from the in-field spectroscopy. At low-power clock laser pumping, the linewidth of the clock spectroscopy is approximately 450 k Hz(full width at half-maximum), which corresponds to a Doppler broadening at the atom temperature of 60 μK. We determine the ~1S_0–~3P_0transition frequency to be 1,128,575,290.819(14) MHz by referencing with a hydrogen maser and measuring with a fiber optical frequency comb. Moreover, a weak Doppler-free signal is observed.     

光纤1/f热噪声的实验研究

光纤热噪声是限制光纤传感、测量系统性能的最终因素.但是低频区域呈1/f谱特性的光纤热噪声的形成机制迄今仍然存在争论.实验研究了光纤1/f热噪声水平与光纤内杂质离子浓度和光纤施加张力的关系,验证了这类热噪声来源于光纤内部的机械耗散引起的长度自发抖动,符合热机械噪声的理论假设.     

All-fiber-based laser with 200 mHz linewidth

We demonstrate the frequency stabilization of a 1.55 μm erbium-doped fiber laser by locking it to a 5-km-long optical fiber delay line(FDL). The stabilized laser is characterized via comparison with a second identical laser system. We obtain a fractional frequency stability of better than 3 × 10~(-15) over time scales of 1–10 s and a laser linewidth of 0.2 Hz, which is the narrowest linewidth of an FDL-stabilized laser observed to date.